In the field of zinc air cells, manufacturers continue to search for ways to create cells with higher voltage, more stable voltage through discharge, better capacity and more cell power to achieve better device functionality.
Anodes of electrochemical cells are prone to electrochemical corrosion, reactions when stored at or above room temperature. The electrolyte in the anode may corrode the anode upon contact, forming oxidized products that decrease the availability of active anode material while simultaneously generating hydrogen gas. The rate of corrosion tends to increase as the electrolyte is made more dilute and as the storage temperature rises, and can lead to a significant decrease in cell capacity. Cell discharge performance, on the other hand, can be improved by making the electrolyte increasingly diluted. It is thus desirable to suppress gas generation when using diluted electrolytes for increased performance.
To minimize undesirable corrosion and gassing during storage, it is typical to employ corrosion-resistant alloys and to reduce the extent of impurities in the anode. Additionally, organic surfactants and inorganic corrosion-inhibiting agents are commonly added to anodes. Surfactants act at the anode-electrolyte interface by forming a hydrophobic film that protects the anode surface during storage. The inhibitive efficiency of surfactants to increase the corrosion resistance of anode material depends on their chemical structure, concentration, and their stability in the electrolyte.
Despite their ability to control gel gassing and cell gassing, many corrosion-inhibiting materials used in the art also typically decrease high rate discharge performance in electrochemical cells and can adversely affect intermittent cell discharge performance. It is believed that discharge performance suffers as a result of anode failure caused by a combination of passivation, hydroxide ion depletion, and reduction in hydroxide ion diffusion. Therefore, new approaches are sought for inhibiting corrosion and preventing leakage, without simultaneously reducing high rate cell discharge performance. At the same time, it is also of interest to develop new classes of surfactants for use in anodes of electrochemical cells. Still further, extension of service life by chemical and physical modifications to the anode without sacrificing improvements in corrosion resistance and electrochemical behavior are also highly sought.
There remains a need, therefore, for a cell that reduces voltage suppression and inhibits corrosion while providing good cell capacity and a higher, stable voltage.